<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>三角形练习</title>
    <style>
      .box{
          position: relative;
          width: 535px;
          height: 197px;
          margin: 100px auto;
          border: 1px solid #2f528f;
          background-color: #4472c4;
      }
      .box1{
          position: absolute;
          top: 72px;
          right: -70px;
          height: 0;
          width: 0;
          font-size: 0;
          line-height: 0;
          border: solid transparent;
          border-width: 18px 36px;
          border-left-color: #4472c4;
      }
    </style>
</head>
<body>
    <div class="box">
        <span class="box1"></span>
    </div>
</body>
</html>